1. Field of the Invention
This invention pertains generally to vibratory gyroscopes, and more particularly to low-power and low-drift MEMS gyroscopes.
2. Description of Related Art
An inertial navigation system (INS) allows determining (i.e., by ‘dead reckoning’) the velocity, position, and orientation of a moving object, without the need for external references. The term ‘dead reckoning’ (DR), also referred to as ‘ded’ for deduced reckoning is the process of calculating a current position based on a previously determined position, or fix, and advancing that position based upon estimates of speed and direction. Inertial navigation systems rely on a computer which processes inputs from motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously update position, orientation, and velocity for the moving object.
MEMS technology enables relatively small and inexpensive inertial sensors that are widely used in applications including, for example, crash detection and dynamic vehicle control, motion sensing in consumer gaming devices, and camera image stabilization. However, the performance limitations of currently available devices generally preclude their widespread adoption in a number of attractive fields such as GPS aided or dead reckoning navigation. High power dissipation of present MEMS gyroscopes limit use in battery powered devices, such as smart phones, while performance issues, such as high drift, limit use for navigation.
Present state-of-the-art MEMS gyroscopes operate based on exciting high amplitude vibrations in one or more directions of a proof mass generally referred to as the drive axe(s). Angular rate is inferred from motion of the proof mass in one or more orthogonal directions, which are usually referred to as sense axe(s). Because the amplitude of the motion in the sense direction(s) is orders-of-magnitude smaller than the motion in the driven direction(s), this has necessitated using power hungry low noise amplification in the sense readout circuitry.
Accordingly, a need exists for a low power and low drift MEMS gyroscope, which overcomes the shortcomings of previous gyroscope approaches.